scholarly journals R5X4 Viruses Are Evolutionary, Functional, and Antigenic Intermediates in the Pathway of a Simian-Human Immunodeficiency Virus Coreceptor Switch

2008 ◽  
Vol 82 (14) ◽  
pp. 7089-7099 ◽  
Author(s):  
Silvana Tasca ◽  
Siu-Hong Ho ◽  
Cecilia Cheng-Mayer
Keyword(s):  
Human Immunodeficiency Virus ◽  
Intermediate Phase ◽  
Target Cells ◽  
V3 Loop ◽  
Cxcr4 Usage ◽  
Loop Sequence ◽  
Immunodeficiency Virus ◽  
Cd4 Binding Site ◽  
Coreceptor Switch ◽  
Switch Variant

ABSTRACT To examine the pathway of the coreceptor switching of CCR5-using (R5) virus to CXCR4-using (X4) virus in simian-human immunodeficiency virus SHIVSF162P3N-infected rhesus macaque BR24, analysis was performed on variants present at 20 weeks postinfection, the time when the signature gp120 V3 loop sequence of the X4 switch variant was first detected by PCR. Unexpectedly, circulating and tissue variants with His/Ile instead of the signature X4 V3 His/Arg insertions predominated at this time point. Phylogenetic analysis of the sequences of the C2 conserved region to the V5 variable loop of the envelope (Env) protein showed that viruses bearing HI insertions represented evolutionary intermediates between the parental SHIVSF162P3N and the final X4 HR switch variant. Functional analyses demonstrated that the HI variants were phenotypic intermediates as well, capable of using both CCR5 and CXCR4 for entry. However, the R5X4 intermediate virus entered CCR5-expressing target cells less efficiently than the parental R5 strain and was more sensitive to both CCR5 and CXCR4 inhibitors than either the parental R5 or the final X4 virus. It was also more sensitive than the parental R5 virus to antibody neutralization, especially to agents directed against the CD4 binding site, but not as sensitive as the late X4 virus. Significantly, the V3 loop sequence that determined CXCR4 use also conferred soluble CD4 neutralization sensitivity. Collectively, the data illustrate that, similar to human immunodeficiency virus type 1 (HIV-1) infection in individuals, the evolution from CCR5 to CXCR4 usage in BR24 transitions through an intermediate phase with reduced virus entry and coreceptor usage efficiencies. The data further support a model linking an open envelope gp120 conformation, better CD4 binding, and expansion to CXCR4 usage.

scholarly journals V2 Loop Glycosylation of the Human Immunodeficiency Virus Type 1 SF162 Envelope Facilitates Interaction of This Protein with CD4 and CCR5 Receptors and Protects the Virus from Neutralization by Anti-V3 Loop and Anti-CD4 Binding Site Antibodies

2000 ◽  
Vol 74 (15) ◽  
pp. 6769-6776 ◽  
Author(s):  
Amy Ly ◽  
Leonidas Stamatatos
Keyword(s):  
Human Immunodeficiency Virus ◽  
Viral Replication ◽  
Binding Site ◽  
Target Cells ◽  
V3 Loop ◽  
Dependent Manner ◽  
Immunodeficiency Virus ◽  
Cd4 Binding Site ◽  
Carboxy Terminal ◽  
In Cells

ABSTRACT We examined the role of asparagine-linked glycosylation of the V2 loop of the human immunodeficiency virus (HIV) SF162 envelope on viral replication potential and neutralization susceptibility. We report that the asparagines located at the amino- and carboxy-terminal sites (at positions 154 and 195, respectively), as well as within the V2 loop of the SF162 envelope (at position 186), are glycosylated during in vitro replication of this virus in human peripheral blood mononuclear cells. Our studies indicate that glycosylation of the V2 loop, in particular at its base, facilitates the interaction of the HIV envelope with the CD4 and CCR5 receptor molecules present on the surface of target cells and affects viral replication kinetics in a cell type-dependent manner. In cells expressing high numbers of receptor molecules on their surfaces, the SF162-derived V2 loop-deglycosylated mutant viruses replicate as efficiently as the parental SF162 virus, while in cells expressing small numbers of receptor molecules, the mutant viruses replicate with markedly reduced efficiency. In addition to expanding the viral tropism, V2 loop glycosylation at the three sites examined prevents neutralization by anti-CD4 binding site antibodies. In contrast, glycosylation at the amino- and carboxy-terminal sites of the V2 loop but not within the loop itself offers protection against anti-V3 loop antibodies. Thus, the epitopes masked by the sugar molecules present on the three glycosylation sites examined are not identical but overlap.

scholarly journals Conserved Changes in Envelope Function during Human Immunodeficiency Virus Type 1 Coreceptor Switching

2007 ◽  
Vol 81 (15) ◽  
pp. 8165-8179 ◽  
Author(s):  
Cristina Pastore ◽  
Rebecca Nedellec ◽  
Alejandra Ramos ◽  
Oliver Hartley ◽  
John L. Miamidian ◽  
...  
Keyword(s):  
Human Immunodeficiency Virus ◽  
Human Immunodeficiency Virus Type ◽  
Virus Type ◽  
Envelope Function ◽  
Site Directed Mutagenesis ◽  
Target Cells ◽  
Immunodeficiency Virus ◽  
Coreceptor Switch ◽  
Soluble Cd4

ABSTRACT We studied the evolution of human immunodeficiency virus type 1 (HIV-1) envelope function during the process of coreceptor switching from CCR5 to CXCR4. Site-directed mutagenesis was used to introduce most of the possible intermediate mutations in the envelope for four distinct coreceptor switch mutants, each with a unique pattern of CCR5 and CXCR4 utilization that extended from highly efficient use of both coreceptors to sole use of CXCR4. Mutated envelopes with some preservation of entry function on either CCR5- or CXCR4-expressing target cells were further characterized for their sensitivity to CCR5 or CXCR4 inhibitors, soluble CD4, and the neutralizing antibodies b12-IgG and 4E10. A subset of mutated envelopes was also studied in direct CD4 or CCR5 binding assays and in envelope-mediated fusion reactions. Coreceptor switch intermediates displayed increased sensitivity to CCR5 inhibitors (except for a few envelopes with mutations in V2 or C2) that correlated with a loss in CCR5 binding. As use of CXCR4 improved, infection mediated by the mutated envelopes became more resistant to soluble CD4 inhibition and direct binding to CD4 increased. These changes were accompanied by increasing resistance to the CXCR4 inhibitor AMD3100. Sensitivity to neutralizing antibody was more variable, although infection of CXCR4-expressing targets was generally more sensitive to neutralization by both b12-IgG and 4E10 than infection of CCR5-expressing target cells. These changes in envelope function were uniform in all four series of envelope mutations and thus were independent of the final use of CCR5 and CXCR4. Decreased CCR5 and increased CD4 binding appear to be common features of coreceptor switch intermediates.

Tin Protoporphyrin IX Used in Control of Heme Metabolism in Humans Effectively Inhibits HIV-1 Infection

1994 ◽  
Vol 5 (5) ◽  
pp. 322-330 ◽  
Author(s):  
A. R. Neurath ◽  
N. Strick ◽  
K. Lin ◽  
A. K. Debnath ◽  
S. Jiang
Keyword(s):  
Protoporphyrin Ix ◽  
V3 Loop ◽  
Gp 120 ◽  
Loop Sequence ◽  
Immunodeficiency Virus ◽  
Cd4 Binding Site ◽  
Glycoprotein Gp120 ◽  
Tin Protoporphyrin ◽  
Hiv 1

Recent observations indicated that several porphyrins bound to the V3 loop of the envelope glycoprotein gp120 of the human immunodeficiency virus type 1 (HIV-1) and inhibited infection of cells by HIV-1. The tin derivative of protoporphyrin IX (Sn-PTP-IX) has already been used clinically in humans to suppress hyperbilirubinemia. It was therefore of interest to determine whether Sn-PTP-IX has anti-HIV-1 activity. It is demonstrated here that Sn-PTP-IX effectively inhibited infection by several HIV-1 isolates (HIB, MN, RF, SF-2 and two isolates resistant to azidothymidine). This was surprising, since earlier studies indicated that incorporation of other metals into porphyrins markedly decreased their antiviral activity. Sn-PTP-IX blocked the binding to gp120 of anti-V3-loop-specific antibodies and of monoclonal antibodies specific for the CD4 binding site on gp120. The latter effect appeared to be allosteric and was not observed with a deletion mutant of gp 120 lacking the V3 loop sequence. This suggests that Sn-PTP-IX binds to the V3 loop and distorts the native conformation of the HIV-1 envelope, thereby preventing infection. These results merit the consideration of Sn-PTP-IX as a prophylactic and chemotherapeutic agent against HIV-1.

scholarly journals Changes in the Immunogenic Properties of Soluble gp140 Human Immunodeficiency Virus Envelope Constructs upon Partial Deletion of the Second Hypervariable Region

2003 ◽  
Vol 77 (4) ◽  
pp. 2310-2320 ◽  
Author(s):  
Indresh K. Srivastava ◽  
Keating VanDorsten ◽  
Lucia Vojtech ◽  
Susan W. Barnett ◽  
Leonidas Stamatatos
Keyword(s):  
Human Immunodeficiency Virus ◽  
Binding Site ◽  
Hypervariable Region ◽  
V3 Loop ◽  
Virus Envelope ◽  
Immunodeficiency Virus ◽  
Cd4 Binding Site ◽  
Hiv Envelope ◽  
Immunogenic Properties ◽  
Hiv 1

ABSTRACT Immunization of macaques with the soluble oligomeric gp140 form of the SF162 envelope (SF162gp140) or with an SF162gp140-derived construct lacking the central region of the V2 loop (ΔV2gp140) results in the generation of high titers of antibodies capable of neutralizing the homologous human immunodeficiency virus type 1 (HIV-1), SF162 virus (Barnett et al. J. Virol. 75 :5526-5540, 2001). However, the ΔV2gp140 immunogen is more effective than the SF162gp140 immunogen in eliciting the generation of antibodies capable of neutralizing heterologous HIV-1 isolates. This indicates that deletion of the V2 loop alters the immunogenicity of the SF162gp140 protein. The present studies were aimed at identifying the envelope regions whose immunogenicity is altered following V2 loop deletion. We report that the antibodies elicited by the SF162gp140 immunogen recognize elements of the V1, V2, and V3 loops, the CD4-binding site, and the C1 and C2 regions on the homologous SF162 gp120. With the exception of the V1 and V2 loops, the same regions are recognized on heterologous gp120 proteins. Surprisingly, although a minority of the SF162gp140-elicited antibodies target the V3 loop on the homologous gp120, the majority of the antibodies elicited by this immunogen that are capable of binding to the heterologous gp120s tested recognize their V3 loops. Deletion of the V2 loop has two effects. First, it alters the immunogenicity of the V3 and V1 loops, and second, it renders the C5 region immunogenic. Although deletion of the V2 loop does not result in an increase in the immunogenicity of the CD4-binding site per se, the relative ratio of anti-CD4-binding site to anti-V3 loop antibodies that bind to the heterologous gp120s tested is higher in sera collected from the ΔV2gp140-immunized animals than in the SF162gp140-immunized animals. Overall, our studies indicate that it is possible to alter the immunogenic structure of the HIV envelope by introducing specific modifications.

scholarly journals Cyanovirin-N Binds to gp120 To Interfere with CD4-Dependent Human Immunodeficiency Virus Type 1 Virion Binding, Fusion, and Infectivity but Does Not Affect the CD4 Binding Site on gp120 or Soluble CD4-Induced Conformational Changes in gp120

1999 ◽  
Vol 73 (5) ◽  
pp. 4360-4371 ◽  
Author(s):  
Mark T. Esser ◽  
Toshiyuki Mori ◽  
Isabelle Mondor ◽  
Quentin J. Sattentau ◽  
Barna Dey ◽  
...  
Keyword(s):  
Human Immunodeficiency Virus ◽  
Conformational Changes ◽  
Target Cell ◽  
Envelope Glycoprotein ◽  
Target Cells ◽  
Immunodeficiency Virus ◽  
Cd4 Binding Site ◽  
Hiv 1 ◽  
Soluble Cd4

ABSTRACT Cyanovirin-N (CV-N), an 11-kDa protein isolated from the cyanobacterium Nostoc ellipsosporum, potently inactivates diverse strains of human immunodeficiency virus type 1 (HIV-1), HIV-2, and simian immunodeficiency virus. While it has been well established that the viral surface envelope glycoprotein gp120 is a molecular target of CV-N, the detailed mechanism of action is of further interest. We compared matched native and CV-N-treated virus preparations in a panel of assays that measure viral replication, assessing successive stages of the viral life cycle. CV-N-treated virions failed to infect cells as detected by p24 production and quantitative PCR for HIV-1 reverse transcription products, whereas treatment of the target cells did not block infection, confirming that CV-N acts at the level of the virus, not the target cell, to abort the initial infection process. Compared to native HIV-1 preparations, CV-N-treated HIV-1 virions showed impaired CD4-dependent binding to CD4+ T cells and did not mediate “fusion from without” of CD4+ target cells. CV-N also blocked HIV envelope glycoprotein Env-induced, CD4-dependent cell-cell fusion. Mapping studies with monoclonal antibodies (MAbs) to defined epitopes on the HIV-1 envelope glycoprotein indicated that CV-N binds to gp120 in a manner that does not occlude or alter the CD4 binding site or V3 loop or other domains on gp120 recognized by defined MAbs and does not interfere with soluble CD4-induced conformational changes in gp120. Binding of CV-N to soluble gp120 or virions inhibited subsequent binding of the unique neutralizing MAb 2G12, which recognizes a glycosylation-dependent epitope. However, prior binding of 2G12 MAb to gp120 did not block subsequent binding by CV-N. These results help clarify the mechanism of action of CV-N and suggest that the compound may act in part by preventing essential interactions between the envelope glycoprotein and target cell receptors. This proposed mechanism is consistent with the extensive activity profile of CV-N against numerous isolates of HIV-1 and other lentiviruses and supports the potential broad utility of this protein as a microbicide to prevent the sexual transmission of HIV.

scholarly journals Adaptive Mutations in a Human Immunodeficiency Virus Type 1 Envelope Protein with a Truncated V3 Loop Restore Function by Improving Interactions with CD4

2009 ◽  
Vol 83 (21) ◽  
pp. 11005-11015 ◽  
Author(s):  
Caroline Agrawal-Gamse ◽  
Fang-Hua Lee ◽  
Beth Haggarty ◽  
Andrea P. O. Jordan ◽  
Yanjie Yi ◽  
...  
Keyword(s):  
Human Immunodeficiency Virus ◽  
Amino Acid ◽  
Binding Site ◽  
Human Immunodeficiency Virus Type ◽  
Envelope Protein ◽  
V3 Loop ◽  
Immunodeficiency Virus ◽  
Cd4 Binding Site ◽  
Hiv 1

ABSTRACT We previously reported that a human immunodeficiency virus type 1 (HIV-1) clade B envelope protein with a severely truncated V3 loop regained function after passage in tissue culture. The adapted virus, termed TA1, retained the V3 truncation, was exquisitely sensitive to neutralization by the CD4 binding site monoclonal antibody b12 and by HIV-positive human sera, used CCR5 to enter cells, and was completely resistant to small molecule CCR5 antagonists. To examine the mechanistic basis for these properties, we singly and in combination introduced each of the 5 mutations from the adapted clone TA1 into the unadapted envelope. We found that single amino acid changes in the C3 region, the V3 loop, and in the fusion peptide were responsible for imparting near-normal levels of envelope function to TA1. T342A, which resulted in the loss of a highly conserved glycosylation site in C3, played the primary role. The adaptive amino acid changes had no impact on CCR5 antagonist resistance but made virus more sensitive to neutralization by antibodies to the CD4 binding site, modestly enhanced affinity for CD4, and made TA1 more responsive to CD4 binding. Specifically, TA1 was triggered by soluble CD4 more readily than the parental Env and, unlike the parental Env, could mediate entry on cells that express low levels of CD4. In contrast, TA1 interacted with CCR5 less efficiently and was highly sensitive to antibodies that bind to the CCR5 N terminus and ECL2. Therefore, enhanced utilization of CD4 is one mechanism by which HIV-1 can overcome mutations in the V3 region that negatively affect CCR5 interactions.

scholarly journals Different Mutational Pathways to CXCR4 Coreceptor Switch of CCR5-Using Simian-Human Immunodeficiency Virus

2008 ◽  
Vol 82 (11) ◽  
pp. 5653-5656 ◽  
Author(s):  
Siu-hong Ho ◽  
Nataliya Trunova ◽  
Agegnehu Gettie ◽  
James Blanchard ◽  
Cecilia Cheng-Mayer
Keyword(s):  
Human Immunodeficiency Virus ◽  
Lymph Node ◽  
Experimental System ◽  
V3 Loop ◽  
Infected Macaque ◽  
Immunodeficiency Virus ◽  
Coreceptor Switch ◽  
Cxcr4 Coreceptor ◽  
Functional Analyses

ABSTRACT We report here a second case of coreceptor switch in R5 simian-human immunodeficiency virus SF162P3N (SHIVSF162P3N)-infected macaque CA28, supporting the use of this experimental system to examine factors that drive the change in coreceptor preference in vivo. Virus recovered from CA28 plasma (SHIVCA28NP) used both CCR5 and CXCR4 for entry, but the virus recovered from lymph node (SHIVCA28NL) used CXCR4 almost exclusively. Sequence and functional analyses showed that mutations in the V3 loop that conferred CXCR4 usage in macaque CA28 differed from those described in the previously reported case, demonstrating divergent mutational pathways for change in the coreceptor preference of the R5 SHIVSF162P3N isolate in vivo.

scholarly journals Determinants of Human Immunodeficiency Virus Type 1 Envelope Glycoprotein Activation by Soluble CD4 and Monoclonal Antibodies

1998 ◽  
Vol 72 (8) ◽  
pp. 6332-6338 ◽  
Author(s):  
Nancy Sullivan ◽  
Ying Sun ◽  
James Binley ◽  
Juliette Lee ◽  
Carlos F. Barbas ◽  
...  
Keyword(s):  
Human Immunodeficiency Virus ◽  
Monoclonal Antibodies ◽  
Envelope Glycoprotein ◽  
Envelope Glycoproteins ◽  
V3 Loop ◽  
Immunodeficiency Virus ◽  
Cd4 Binding Site ◽  
Hiv 1 ◽  
Soluble Cd4

ABSTRACT Infection by some human immunodeficiency virus type 1 (HIV-1) isolates is enhanced by the binding of subneutralizing concentrations of soluble receptor, soluble CD4 (sCD4), or monoclonal antibodies directed against the viral envelope glycoproteins. In this work, we studied the abilities of different antibodies to mediate activation of the envelope glycoproteins of a primary HIV-1 isolate, YU2, and identified the regions of gp120 envelope glycoprotein contributing to activation. Binding of antibodies to a variety of epitopes on gp120, including the CD4 binding site, the third variable (V3) loop, and CD4-induced epitopes, enhanced the entry of viruses containing YU2 envelope glycoproteins. Fab fragments of antibodies directed against either the CD4 binding site or V3 loop also activated YU2 virus infection. The activation phenotype was conferred on the envelope glycoproteins of a laboratory-adapted HIV-1 isolate (HXBc2) by replacing the gp120 V3 loop or V1/V2 and V3 loops with those of the YU2 virus. Infection by the YU2 virus in the presence of activating antibodies remained inhibitable by macrophage inhibitory protein 1β, indicating dependence on the CCR5 coreceptor on the target cells. Thus, antibody enhancement of YU2 entry involves neither Fc receptor binding nor envelope glycoprotein cross-linking, is determined by the same variable loops that dictate enhancement by sCD4, and probably proceeds by a process fundamentally similar to the receptor-activated virus entry pathway.

scholarly journals Variable Constraints on the Principal Immunodominant Domain of the Transmembrane Glycoprotein of Human Immunodeficiency Virus Type 1

1999 ◽  
Vol 73 (7) ◽  
pp. 5698-5706 ◽  
Author(s):  
Rastine Merat ◽  
Herve Raoul ◽  
Thierry Leste-Lasserre ◽  
Pierre Sonigo ◽  
Gianfranco Pancino
Keyword(s):  
Human Immunodeficiency Virus ◽  
Human Immunodeficiency Virus Type ◽  
Virus Type ◽  
Surface Glycoprotein ◽  
Target Cells ◽  
Transmembrane Glycoprotein ◽  
Loop Sequence ◽  
Immunodeficiency Virus ◽  
Hiv 1

ABSTRACT Lentiviruses have in their transmembrane glycoprotein (TM) a highly immunogenic structure referred to as the principal immunodominant domain (PID). The PID forms a loop of 5 to 7 amino acids between two conserved cysteines. Previous studies showed that envelope (Env) glycoprotein functions of feline immunodeficiency virus (FIV) could be retained after extensive mutation of the PID loop sequence, in spite of its high conservation. In order to compare Env function in different lentiviruses, either random mutations were introduced in the PID loop sequence of human immunodeficiency virus type 1 (HIV-1) or the entire HIV-1 PID loop was replaced by the corresponding PID loop of FIV or simian immunodeficiency virus (SIV). In the macrophage-tropic HIV-1 ADA Env, mutations impaired the processing of the gp160 Env precursor, thereby abolishing viral infectivity. However, 6 of the 108 random Env mutants that were screened retained the capacity to induce cell membrane fusion. The SIV and FIV sequences and five random mutations were then introduced in the context of T-cell-line-adapted HIV-1 LAI which, although phenotypically distant from HIV-1 ADA, has an identical PID loop sequence. In contrast to the situation for HIV-1 ADA mutants, the cleavage of the Env precursor was unaffected in most HIV-1 LAI mutants. Such mutations, however, resulted in increased shedding of the gp120 surface glycoprotein (SU) from the gp41 TM. The HIV-1 LAI Env mutants showed high fusogenic efficiency. Three Env mutants retained the capacity to mediate virus entry in target cells, although less efficiently than the wild-type Env, and allowed the reconstitution of infectious molecular clones. These results indicated that in HIV-1, like FIV, the conserved PID sequence can be changed without impairing Env function. However, functional constraints on the PID of HIV-1 vary depending on the structural context of Env, presumably in relation to the role of the PID in the interaction of the SU and TM subunits and the stability of the Env complex.

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